Inner Interfaces

[Sahil Kapoor]

I have read a line in Khalid Mughal and it states that

"Nested Interfaces are always static ".

I executed the following and it compiled okay.

class InnerInterface {

  interface weapons {
    
  }
  
  
  
}
    

Please do confirm the above statement, is it wrong or wrongly interpreted by me ???

Thanks !!!

2) Please do consider statement

" No other static memebers, except final static fields, can be declared within a non-static member class"

This statement is given Correct. But i tried the follwing code snippet and it failed to compile.

  class Outer {
 
  class Inner {
   static final int a;
  }
}  

So, please do confirm this statement too.... In my consideration , the above statement is false.

Thanks !!!

[Abimaran Kugathasan]

Sahil Rally wrote:I have read a line in Khalid Mughal and it states that

"Nested Interfaces are always static ".

I executed the following and it compiled okay.

class InnerInterface {

  interface weapons {
    
  }
  
  
  
}
    

Please do confirm the above statement, is it wrong or wrongly interpreted by me ???

Thanks !!!

2) Please do consider statement

" No other static memebers, except final static fields, can be declared within a non-static member class"

This statement is given Correct. But i tried the follwing code snippet and it failed to compile.

  class Outer {
 
  class Inner {
   static final int a;
  }
}  

So, please do confirm this statement too.... In my consideration , the above statement is false.

Thanks !!!

Your first question isn't clear..

For the second, It's the problem related with the initialization of final fields.... Not related to the inner class...

Final variable should be initialized when the declared or in every Constructor of the class

Hope this helps~!

[Abimaran Kugathasan]

And since the inner class can have static final fields, rather than final field, they(static final fields) are compile time time constants. So you can't initialize them in Constructors rather than on the declaration time..

class Outer	{

 	final int ab;

	Outer()	{
		ab = 9; // [This is Ok...But if you have more than one
		//Constructor, then you need to initialize them in every Constructors]
	}
	class Inner	{
		static final int a = 9;
		//static final b; --- [You can't leave a static final
		//fields, without initialize in declaration line].

		public Inner() {
			//b = 5;---- Won't work
		}
	}


}

[Mike Simmons]

For the first question, nested interfaces are always implicitly static. Meaning they're automatically static even if you don't declare them as static.

For the second question, I don't understand your confusion. The statement was made that a non-static member class cannot have any static fields, unless they are either inherited or they are compile-time constants (which is what Abimaran describes). You tried to make a non-static member class with a static field. It didn't compile. The error message you get is "inner classes cannot have static declarations". So what's the problem? Mughal & Rasmussen said you can't do this, and the compiler also told you that you can't do this. M&R are correct.

[Sahil Kapoor]

@both Thanks i got it !!!
Cheers!!!

[Sandra Bachan]

I haven't studied inner classes yet, but what is the design logic for the Java programming language NOT to allow inner classes to have static declarations. Is there only ONE instance of an inner class, hence there is no need to have any static variables? Please clarify.